They won't withstand a direct hit. They're hardened but not against that. It would have to be inside a mountain like NORAD. The plan was always to get them off

They won't withstand a direct hit. They're hardened but not against that. It would have to be inside a mountain like NORAD. The plan was always to get them off the ground before most of the enemy missiles hit. And perhaps to withstand a nearby attack, as targeting tech in the 60s was not very accurate yet. But these days that won't work anymore.